A D-dimer test measures the level of D-dimer in a sample of your blood. D-dimer is a small protein fragment that is made when a blood clot dissolves in the body, and it is normally present only in low amounts. The test is done on a simple blood draw and generally needs no special preparation. This is general health information, not medical advice.
A clinician may order a D-dimer test to help check whether you might have a blood clot and to help decide whether further testing is needed. It may be used when there are symptoms that could point to a clot — for example, swelling, pain, warmth, or color changes in a leg or arm, or sharp chest pain, trouble breathing, coughing up blood, or a fast heartbeat. Conditions it may be used in connection with include deep vein thrombosis (DVT, a clot in a deep vein, often in the lower leg), pulmonary embolism (PE, a blockage in an artery in the lung), and disseminated intravascular coagulation (DIC, a condition in which too many clots form); it may also help monitor how well treatment for DIC is working. The test does not show where a clot is or why it formed.
D-dimer results are commonly reported as "negative" (low or normal) or "positive" (higher than normal). Any specific numeric cutoff or reference range is general only and can vary depending on the laboratory, the testing method used, and factors such as age and sex. Because of this, the reference range printed on your own lab report is what applies to your result — not any general figure. A result should never be read on its own as a personal diagnosis.
A higher-than-normal (positive) D-dimer level may suggest that the body is making or breaking down blood clots, and can be seen with clotting-related conditions such as DVT, PE, or DIC. However, a raised D-dimer level is not specific and is not always caused by a clotting disorder. Higher levels can also be seen with, for example, pregnancy, recent surgery or trauma, heart disease, liver disease, rheumatoid arthritis, higher blood lipid or triglyceride levels, being older (such as over 80), or being immobilized. This is a general list of possible associations, not a complete list and not a diagnosis. Because of this, the test is often most useful when it is negative, or when other causes of a raised level can be ruled out. Additional tests are usually needed to show where a clot is or what type of clotting disorder may be present.
A low or normal (negative) D-dimer result suggests that you probably do not have a problem with blood clotting at the time of testing. "Low" is not typically reported as an abnormal finding for this test. When treatment for DIC is being monitored, a normal or decreasing D-dimer level may suggest that the treatment is working. A clinician interprets a D-dimer result in the full context of your symptoms, medical history, and other tests — no single result is a diagnosis on its own. Talk with your healthcare provider about what your result means for you.
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.